Field of the Invention
The present invention relates generally to desalination systems of the type used in sea going vessels and small watermaker systems to produce fresh water from sea water or brackish water, and particularly, to a means and apparatus for killing and preventing algae and bacteria from growing in the piping, filtering and pumping components of such systems during periods of non-use.
Description of the Prior Art
Because seagoing vessels can only carry limited amounts of fresh water in their holding tanks, long voyages can be constrained by how much fresh water can be carried before having to replenish. Thus, for many years, watermaking systems have been provided using various filtration techniques and processes to produce potable water from seawater. Such processes range from the use of very coarse filtering devices that merely strain out solids, to advanced filtration systems incorporating reverse osmosis (RO) membranes that can remove fine colloids and particulates to produce clear, fresh water permeate or “product water”.
One such RO system is disclosed in my prior U.S. Pat. No. 7,229,555 entitled “Low-maintenance Watermaker” issued Jun. 12, 2007 and expressly incorporated herein by reference. The described water treatment system consists of a pre-filtration system including one or more pump or pumps and filter elements, and a spiral wound RO membrane in a pressure vessel. A reverse osmosis system of such type is subject to long periods of non-use in which water stands in the feed water flow path. As a consequence, during the system shutdown, bacteria and algae can grow in the piping, filter apparatus, pumps and membrane, rendering the system inoperable or inefficient. Moreover, the bacteria often goes anaerobic producing hydrogen sulfide which will permeate through the RO membrane and contaminate the product water.
Often a fresh water flush system is installed to flood the system during shutdown to reduce the bacterial and algae counts and reduce the effects of corrosion due to the salts in the system. And if the system is to be decommissioned or shut down for more than a few days, chemicals are usually circulated through the feed water flow path to sterilize and prevent the growth of bio film from the bacteria and algae resident therein. But such maintenance is expensive, inconvenient, and time consuming, and long periods of non-use without proper advance attention can result in serious systemic corrosion and contamination as well as biofouling of the RO membranes.
However, it has been found that by adding copper and silver ions, or in some cases just copper or just silver ions into the flush water during the shutdown of the system, the bacteria that attack the membrane and produce hydrogen sulfide can be killed without the introduction of harsh chemicals to the system. Moreover, the introduction of the ions can be made fully automatic and not require the system operator to mix and apply treatment chemicals, and perform the storage procedures required such chemicals are used.
It is therefore an objective of the present invention to provide an algae and bacteria contamination abatement means and apparatus for simplifying the preventive maintenance process by using an electrolytic method and apparatus to produce and introduce ions into a stream of flush water during the system shutdown process so as to flood the system plumbing, pumping and filtering components with metallic ions to kill any resident bio organisms.
Another objective of the present invention is to provide a novel algae and bacteria contamination preventing apparatus and subsystem including means for allowing previously generated potable water to be used to batch produce ion carrying fluid for introduction into a watermaker system during its normal shutdown process.
Still another objective of the present invention is to provide a novel algae and bacteria contamination abatement subsystem including a dual functioning filter/ion-generator component for simultaneously removing any vestiges of chlorine from potable water used as the flush water and electrolytically generating and introducing copper and/or silver ions into the water.